Boring machines

ABSTRACT

Apparatus for supporting the boring or cutting tools of a boring machine comprising a rotatable spindle, a carrier mounted at one end of the spindle, and a tool holder extending from the carrier. An arm extends rearwardly from the tool holder into engagement with means for pivoting it. A tool holder is connected to the carrier by at least one torsion bar spring defining the swing axis of the tool holder and exerting a restorative force when twisted.

United States Patent 1 1 1111 3,749,508

Schukrafft July 31, 1973 541 BORING MACHINES 2,134,402 2/1956 Hoem 90/18[75] Inventor: Friedrich Schukmf, Bietigheim 2,438,741 3/l948 Coulson408/154 Germany [73] Assignee: Ludwigsburger Maschiuenbau PrimaryErqmjner-Gil Weidenfeld GmbH, Ludwigsburg, Germany Attorney-Richard Lowand Murray Schaffer et al.

[22] Filed: Aug. 9, 1971 [21] Appl. N0.: 170,104

[57] ABSTRACT [30] Foreign Application Priority Data Aug. 12, 1970Germany P 20 40 020.8 ppar tus f r supporting the boring or cuttingtools of a boring machine comprising a rotatable spindle, a car- [52]us. Cl 408/156, 408/11, 408/156, ri r mounted at one end of h pin and al 408/159, 408/180 holder extending from the carrier. An arm extends[51] Int. Cl B23b 29/034, B23b 51/00 r ly m h l holder into engagementwith [58] Field of Search 408/180, 159, 156, means f r p ng i A l holderis connected to the 408/154, 714, 155, 168, 13, 11, 8 carrier by atleast one torsion bar spring defining the swing axis of the tool holderand exerting a restorative {56] References Cited force when twisted.

UNITED STATES PATENTS 2,412,038 12/1946 Freisen 408/156 7 Claims, 4Drawing Figures PATENIEU JUL 3 1 191a SHEET 1 BF 3 I PATENIEUJUUI ma 4,5

SHEET 2 OF 3 Fig. 2

BORING MACHINES BACKGROUND OF THE INVENTION The present inventionrelates to drilling and boring units for fine precision work and inparticular with apparatus and system for mounting the chisels or worktools on a holder therefor so that they might be deviated along a swingaxis.

In drilling and boring machines of the type here under discussion, arotatable spindle is provided with tool holder at its outer end. Thetool holder is swingable in a transverse direction with respect to thespindle axis. The tool holder carries at least one cutting tool and isprovided with elongated arm by which it is deviated from the spindleaxis. The arm generally extends into the central bore of the spindle andcollaborates with an adjustment member axially slideable within thespindle. The adjustment member acts on the swing arm to swing or deviatethe tool holder about the swing axis. Resilient spring means areprovided to maintain and to urge the tool holder back to its originalposition.

In the known constructions of boring machines of this type, theresilient spring returning action on the swing arm is produced by suchspring means as compression or coil springs. In most cases the springelasticity is not sufficient, particularly at the high speed rotation ofthe spindle, to keep the tool holder in the desired angular positionpreset by the swing adjustment mechanism. Because of this instability,high speed rotation does not produce the accuracy and precision requiredfor the fine boring work necessary in modern technology.

It is the object of the present invention to provide means for holdingboring tool of the type described which overcomes the defects of theknown construction and which provides for the precision and accuracyneeded. It is a further object of the present invention to provide anadjustable tool holder having a sufficiently large resilient restorativeforce enabling the stabilization of the tool holder at high rotationalspeeds in its preset position.

Further advantages and objects of the present invention will be obviousfrom the following disclosure.

SUMMARY OF THE INVENTION According to the present invention, a toolholder is connected by a spindle head by at least one torsion bar springdefining the transverse swing axis for the adjustable swing of theholder.

According to the present invention apparatus is provided for supportingthe boring or cutting tools comprising a rotatable spindle, a carriermounted at one end of the spindle, and a tool holder extending from thecarrier. An arm extends rearwardly from the tool holder into engagementwith means for pivoting it. The tool holder is connected to the carrierby at least one torsion bar spring defining the swing axis of the toolholder and exerting a restorative force when twisted.

Preferably two torsion bars are provided arranged diametrically opposedto each other. To effect this the carrier is formed with an outer ringflange and an inner body portion receiving the tool holder. The twotorsion bars being formed along an axis transverse to the spindle axisand to the plane in which the arm is pivoted.

Adjustable means for pivoting the arm is provided comprising a linearlymoveable rod which is bifurcated to encompass the arm. The rod isprovided with a wedge surface which variously pivots the arm when therod is reciprocated.

Other features and full details of the present invention are disclosedin the following description as shown in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a longitudinal section through a spindle head of a boringmachine made in accordance with the present invention;

FIG. 2 is a view similar to that of FIG. I turned by about thelongitudinal axis of the device;

FIG. 3 is a sectional view taken along lines 3-3 of FIG. 1 in a largerscale than FIG. 1;

FIG. 4 is a sectional view taken along line 4-4 of FIG. 1, alsoenlarged.

DESCRIPTION OF INVENTION Only some of the details of a drilling andboring machine as is necessary to illustrate the inventive tool holderis shown and described. The general construction of boring and drillingmachines including the means for driving the spindle, regulating thespeed and direction of the drill and other well-known features areomitted from this disclosure for the sake of brevity and conciseness.

Turning now to FIG. 1, only the forwardmost bearing of the two or morebearings needed to journal the rotating drive spindles generallydepicted by the numeral 12 is shown. The spindle comprises a hollowshaft 14 journalled at its rearmost end within the bearing 10 andseveral individual part, namely: a hollow cylindrical sleeve 16 which isfixed at its rear edges by suitable screw or bolts to the frontal faceof a radially extending flange l8. Mounted by the same screw or bolts tothe frontal edge of the cylinder 16 is a tool holder carrier generallydefined by the numeral 20. The carrier 20 is adapted to receive in arecess concentric of its central axis a tool holder generally defined bythe numeral 22 which comprises a forwardly extending elongated shaft 24at the outermost end of which two chisels or cutting tools 26 and 28 areinserted. The cutting tools are set in opposite directions and aretransversely adjustable with respect to the surface of the shaft 24. Onrotation of the spindle 12 the chisels cut a hole in a workpiece along apredetermined path, determined in part by the angular disposition givento the tool holder 22 by the positioning of the carrier 20.

The carrier 20 comprises a flat circular disc-like outer flange portion30 and a central body portion 32 from which an integral arm,constituting the lever arm of the carrier, extends rearwardly. The leverarm 34 extends within the central bore 36 of the spindle shaft l4. Apair of diametrically opposed cutout portions 38 are formed in thecarrier 20 between the outer flange 30 and the inner body 32. As seen inFIG. 3 the grooves 38 have an arcuate central section and a pair oflaterally extending radial slits 44, 46, and 44', 46. The central bodyportion 32 is thus connected to the outer flange portion 30 by a pair ofradially extending winglike lateral members 40 and 42 which because ofthe groove 38, constitute a torsion bar spring. The lateral members 40and 42 are diametrically opposed to each other and lie crosswise of thecarrier 20 along the axis transverse to the axis of the swing arm 34.The slots 38 and the lateral slots 40, 46, and 44', 46 are sufficientlywide to provide a degree of radial play between the inner body portion32 and the outer annular flange portion 30 as well as to permit the body32 to resiliently twist or flex about the transverse axis runningthrough the torsion bars 40 and 42.

The carrier, as seen in the preceeding description, can in its entiretybe fashioned from a single piece of bar stock including the rearwardlydirected arm 34 and then enlarged central body portion 32. The arcuategrooves 38 and the slits 44, 46, and 44', 46' can all be symmetricallycut from the single workpiece to provide the structure shown.

The tool holder 22 is itself provided with an enlarged rearward directedend 50 which seats within a socket 52 formed concentrically in thefrontal face of the body portion 32 ofthe carrier 20. The tool holder 22is also provided with a radially extending retaining flange 48 whichseats against the frontal face and edge of the body portion 32 so as tobe firmly seated hereon. A retaining flange 48 is fastened to the bodyportion 32 of the carrier by suitable screw means. An outer centering orcoping ring 52 is provided which is itself screwed to the frontal faceof the flange portion of the carrier 20. The inner circumference of thecentering ring 54 is grooved or undercut and is provided with a sealingwasher such as resilient O-ring 56 which acts to seal the space betweenthe centering ring and the re taining plate 48. The washer 56 preventsdirt, oil, metal chips, and other contaminants from reaching theinterior of the spindle head.

The lever arm 34, extending from and integral with the body 32 of thecarrier 20, extends as mentioned earlier into the bore 36 of the spindleshaft 14. Extending from the machine proper, or from the other end ofthe shaft 14, into the bore 36 and in engagement with the arm 34 is aswing adjustment member generally defined by the numeral 60. A rotary tolinear translating mechanism including a bar 62 provided with a screw atits frontal end is threaded within a central bore in the rear end of theswing adjustment member 60. The bar 62 is connected to conventionalwhereby it may be rotated to effect the linear adjustment of the swingadjustment member 60. The adjustment member 60 comprises an elongatedbar, bifurcated along its longitudinal axis and having a pair of opposedarms 64 and 66 extending in the direction of an actually overlapping thelever arm 34. At its rearward end the lever arm 34 is provided with twoflat faces 68 and 70, conforming to and cooperating with the interiorsurfaces of the arms 64 and 66 of the adjustment member 60. One of theforked arms of the adjustment member 60, namely: the arm 66 is providedwith an inclined surface 72 directed towardthe flat side 68 of the leverarm 34. As seen in FIG. I, the inclined surface 72 is larger at itsrearward end opening in an angle in that direction, forming a wedgewhich coacts with a slide insert piece 74 inset into arm 34. The slidepiece 74 is made of hard metal material and is set within a groove inthe flat surface 68 of the arm 34 by a set screw. it is to be noted thatthe dimensions of the space between the inner surfaces of the bifurcatedarms 64 and 66 and the distance between the surfaces 68 and 70 of theswing arm 34 are such that a small space remains between the surface ofthe bifurcated arm 64 and the flat surface 70 of the arm 34. That is,that a distance is maintained between these two surfaces which permitsthe swing adjustment member 60 and the arm 34 to control means pivotrelatively to each other about a fulcrum point associated with the slidepiece 74. To permit ever greater pivoting the heel of the lever arm isbevelled. It is to be noted that the flat surfaces 68 and are in adirection transverse to that of the axis of the torsion bar and in aplane perpendicular to an axis drawn through the center of the arcuatecut out portions 38.

As indicated in FIG. 2, the adjustment member is re-- ciprocably movablevirtually the entire distance over the flattened portions of the leverarm 34 from a rearmost position shown in the full lines to theforwardmost position shown in the dot-dash lines. Thus, because of theinclined planar surface 72, coacting with the wedge piece 74, the leverarm 34 can be made to pivot or turn and in turn itself cause the bodyportion 32 of the carrier 20 to pivot in an axis through the torsion barsprings 40 and 42. The torque created in the torsion bar is so effectivethat any deviation from the preset adjusted position created by themember 60 pivoting the arm 34 will be overcome and the tool holder willthereby maintain its angular direction throughout the cutting operation.Consequently the tool holder 22 is adjustable in the radial direction byeven the smallest amounts and held therein by the adjustment member 60.The bar springs 40 and 42 thus revolve or twist about their axis,twisting the material of which they are made and thereby automaticallysetting up a resilient restoring torque of a force sufficient to tend toreturn the body 32 to its original normal rest position.

The automatic restoring action can be controlled by the use of a sensingdevice 76 indicated in the dot-dash lines in FIG. 1. The sensing devicemay be fastened to a holder 78, which can be fixedly attached to theouter surface of the spindle head. The holder 78 may, for example, alsobe magnetic and therefore be self-adherent to the spindle head. Thesensing device can sense the angular position of the working tools 26and 28 and therefore the position of the head 22 and produce a signalwhich may be converted to control the adjustment shaft 62 positioningthe control member 60 as desired selectively along the swing arm 34 toeffect the desired compensation and perfect operation.

It will thus be seen from the foregoing description of the presentdevice that the tool holder 22 is secured within a central body portion32 which is connected to the main carrier 20 by at least one torsion barspring defining the swing axis of the tool holder. Through the use ofsuch a torsion bar spring device, the spindle head has considerablylarger resilient and restorative powers allowing the spindle head to beturned and preset to the operating position and maintained there duringcutting at a faster and securer rate than with the use of the customarycoil or compression springs. The torsion bar spring has a progressivelyincreasing stiffness and torque resulting from the increase of stressplaced upon it. Thus the more the lever arm increases in angulardeviation from its normal position, the greater the restoring torquecreated. Thus even considerably short or small angular deviations andeven at extraordinarily high speeds of rotation, the spindle head may bestabilized quickly and efficiently.

Various modifications of the preceeding construction can be made. It is,for example, possible to use a round rod rather than a bar shaped memberfor the torsion spring. The round rod may be formed in the same manneras a rectangular bar as previously described, i.e., as an integral partof a one piece carrier member. On the other hand, the carrier may bemade of several pieces with the round bar stock anchored both in thecentral body portion and the outer flange member. The povision ofa pairof oppositely arranged torsion springs is most advantageous since thisconstruction is simple and provides the symmetry and stability necessaryunder high speed rotation.

The aforementioned construction has the further advantage of permittingan effective seal through the use of an O-ring washer between theradially outer centering ring member and the inner flange memberretaining ring of the holder 22. This arrangement permits the holder 22to be easily removed and replaced with a similar unit, without having todissassemble the entire spindle head. The new tool holder can bereplaced in the socket 52 of the body 32 of the carrier 20 and an O-ring56 easily inserted.

The bifurcated adjustment member 60 has the further advantage in thatits shape and form does not require the use of any external or extramass compensating means. Under normal conditions, the known means forswinging the tool holder would create an imbalance of the mass in therotating spindle and mass compensating means would have to be provided.Because the lever arm 34 extends between the bifurcated arms of theadjustment member 60, one of the arms form the adjustment wedge orinclined surface while the other arm can be built to compensate for theadded weight.

What is claimed 1. Apparatus for supporting the tool of a boring device,comprising a rotatable spindle having a central axis, a carrier mountedat one end of said spindle, a tool holder extending from said carrierand holding said boring tools, an arm extending rearwardly from saidtool holder, means engaging said arm for swinging said arm to pivot saidtool holder within said carrier, said tool holder being connected tosaid carrier by a pair of diametrically opposed torsion bar springsextending along an axis transverse to the axis of said spindle definingthe swing axis of said tool holder and exerting a restoring torque forcethereon when twisted.

2. The apparatus according to claim 1 wherein said spindle is hollowhaving a central longitudinal bore into which the arm extends andwherein the means for swinging said arm comprises a linearlyreciprocable rod engaging said arm, said rod and said arm havingcooperating wedge surfaces adapted to adjust the position of said arm onmovement of said rod.

3. The apparatus according to claim 2 including means for automaticallyreciprocating said adjustment rod.

4. The apparatus according to claim 1 including a head at the frontalend of said spindle, the carrier comprising an outer ring flange securedto said head, and an inner body spaced from said flange and adapted tosupport the tool holder, said body being connected to said ring flangeby said pair of diametrically opposed torsion bar springs integrallysecured to both said ring flange and said body and forming the swingaxis of said tool holder, said body having the rearwardly extending armintegrally formed therewith.

S. The apparatus according to claim 1 wherein the body has a centralopening in its frontal face adapted to receive the tool holder, saidtool holder including an annular flange and means securing said flangeto said body.

centering ring encompassing the flange of the tool holder, saidcentering ring being secured to the ring flange of the carrier andincluding washer means seated between said centering flange and the toolholder flange to seal the same.

7. The apparatus according to claim 2 wherein the adjustment rodcomprises a bifurcated member in which the arm is received, one of thebifurcated arms having an inclined surface forming a wedge adjacent onesurface of said arm, a slide member secured to the one surface of saidarm to engage said wedge.

6. The apparatus according to claim 5 including a

1. Apparatus for supporting the tool of a boring device, comprising arotatable spindle having a central axis, a carrier mounted at one end ofsaid spindle, a tool holder extending from said carrier and holding saidboring tools, an arm extending rearwardly from said tool holder, meansengaging said arm for swinging said arm to pivot said tool holder withinsaid carrier, said tool holder being connected to said carrier by a pairof diametrically opposed torsion bar springs extending along an axistransverse to the axis of said spindle defining the swing axis of saidtool holder and exerting a restoring torque force thereon when twisted.2. The apparatus according to claim 1 wherein said spindle is hollowhaving a central longitudinal bore into which the arm extends andwherein the means for swinging said arm comprises a linearlyreciprocable rod engaging said arm, said rod and said arm havingcooperating wedge surfaces adapted to adjust the position of said arm onmovement of said rod.
 3. The apparatus according to claim 2 includingmeans for automatically reciprocating said adjustment rod.
 4. Theapparatus according to claim 1 including a head at the frontal end ofsaid spindle, the carrier comprising an outer ring flange secured tosaid head, and an inner body spaced from said flange and adapted tosupport the tool holder, said body being connected to said ring flangeby said pair of diametrically opposed torsion bar springs integrallysecured to both said ring flange and said body and forming the swingaxis of said tool holder, said body having the rearwardly extending armintegrally formed therewith.
 5. The apparatus according to claim 1wherein the body has a central opening in its frontal face adapted toreceive the tool holder, said tool holder including an annular flangeand means securing said flange to said body.
 6. The apparatus accordingto claim 5 including a centering ring encompassing the flange of thetool holder, said centering ring being secured to the ring flange of thecarrier and including washer means seated between said centering flangeand the tool holder flange to seal the same.
 7. The apparatus accordingto claim 2 wherein the adjustment rod comprises a bifurcated member inwhich the arm is received, one of the bifurcated arms having an inclinedsurface forming a wedge adjacent one surface of said arm, a slide membersecured to the one surface of said arm to engage said wedge.